“This shows mostly Spanish, Dutch, and English routes — they are surprisingly constant over the period (although some empires drop in and out of the record), but the individual voyages are fun. And there are some macro patterns — the move of British trade towards India, the effect of the American Revolution and the Napoleonic Wars, and so on.”

Schmidt has another visualization on his blog that breaks down the data based on seasonal patterns. A grad student at Princeton, Schmidt admits that “19th century ocean trade isn’t exactly much my field,” but he does offers some insights into why the maps look this way and what’s missing (Darwin’s Beagle, U.S. data, and so on).

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This post is part of an ongoing series exploring visualizations. We’re always looking for leads, so please drop a line if there’s a visualization you think we should know about.